Orthogonal test method is used to study the effect of the mineral admixtures on the performance of FGD gypsum-fly ash complex cementing material. On the basic experiment, the effect of the traditional alkali and salt admixtures added to the complex cementitious system is discussed, the factors effecting on performance of the FGD gypsum were analyzed. Based on the experimental results, the best mix proportion was determined. Finally, the basic performance of complex cementitious material was tested. The experimental results show that the performance of FGD gypsum which is activated through adding the compound admixtures was similar with the ordinary interior wall materials. The strength and water resistance of FGD gypsum complex cementing material can be greatly enhanced by adding cement, quicklime and slag powder, and effect of cement is largest, and slag smallest. The performance of the gypsum complex cementing material also can be improved after incorporation of a few of chemical admixture on the basis of adding mineral activators.